JPH0568144A - Digital image forming device - Google Patents

Abstract

PURPOSE:To suppress the wasteful use of a developer and to shorten time required up to the formation of an image by forward moving a traveling body at the time of detecting the use of a manual feeding system, and moving the traveling body up to a prescribed position until the setting of transfer paper is completed. CONSTITUTION:When a detection output detects the use of manual feeding systems 33a, 33b, the driving of the traveling body 10 is most effectively controlled up to a scanning position. When an image forming instruction is outputted from an instruction means, the traveling body 10 is controlled so as to be driven from a maximum sub-scanning position P to a prescribed home position HP. At the time of driving the body 10, a signal obtained by the exposure scanning of an original is outputted to a size detecting means 33S and the body 10 is driven in accordance with a detected original size. A white plate to be a reference is arranged on a position between the home position HP for starting the movement of the body 10 up to the starting position of an original reader 100. Gain is set up so that the output of an image sensor 9 due to reflected light from the reference white plate is amplified to a prescribed voltage level. Consequently the wasteful use of the developer can be suppressed time required up to the formation of an image can be shortened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital image forming apparatus, and more particularly to a digital image forming apparatus having a manual sheet feeding function.

[0002]

2. Description of the Related Art A conventional digital image forming apparatus, such as a digital copying machine, has a plurality of trays for accommodating transfer sheets, and transfer sheets of different sizes can be set for each tray. Normally, a user can select a required tray according to the document size according to an instruction. Further, in recent years, there is a copying machine having a function of detecting the size of a set original and automatically selecting and feeding a tray on which a transfer paper to be fed corresponding to the original size is set (for example, (Kaisho 63-280569). In such an apparatus, when the print key is pressed, the scanner is scanned to detect the document size, and after the scanner returns to the home position, scanning corresponding to the document size is performed to form an image.

[0003]

In the apparatus having the size detecting function as described above, when the transfer sheet is fed by manual feeding, the transfer sheet used by the user is arbitrarily prepared in accordance with the document size. There is no need to detect the size of the original to automatically select and transfer the transfer paper, and the detection of the original size was automatically canceled. Further, in the case of manual feeding, various papers (original and transfer paper) are used by the user, and the scanner scanning is a full scan so that various original sizes can be dealt with when scanning the original. .. For this reason, when the document size is smaller than the full scan area, the scanner scanning is performed over a wider area than the document size area, and the entire area to be scanned must be covered by using the pressure plate or the like. The developer adheres to the outside of the upper original size area, and the developer is wasted. In particular, since it is difficult to use a pressure plate or the like for a book document, it is easy to waste the developer. Therefore, even when the transfer paper is fed by manual feeding, the scanner is driven back and forth once to detect the above-mentioned document size, and only the image signal in the document size area is extracted by the next scanner forward drive. By forming the image based on the above, the above-mentioned problem is improved.

SUMMARY OF THE INVENTION It is an object of the present invention to suppress the wasteful use of a developer in image formation by manual paper feeding and to shorten the time from the image formation instruction to the start of image formation.

[0005]

In a digital image forming apparatus of the present invention, a traveling body (10) equipped with illumination means (2a, 2b) extending in the main scanning direction is driven in the sub scanning direction to expose and scan a document. Image reading means (100) for reading signals corresponding to the original pixels;
Size detecting means (101, 102, 300) for detecting the document size from the signal read by the image reading means (100); Image reading means (10
Image forming means for forming an image on a transfer sheet fed to a predetermined position at a predetermined timing in response to the signal read by (0)
(200); Instructing means (41) for instructing image formation; Manual paper feed system (33c, 37a) for manually feeding transfer paper set at a predetermined position at a predetermined timing; Manual paper feed system (33c, 37a) )
Detection means (33s) for detecting the use / non-use of
When (s) detects the use of the manual paper feed system (33c, 37a), the traveling body (10) is drive-controlled to the maximum sub-scanning position (P), and if the image forming instruction is given by the instruction means (41), the maximum Sub scanning position
(P) drives the traveling body (10) in the direction of the predetermined home position (HP), and outputs a signal obtained by exposing and scanning the document at the time of driving to the size detecting means (101, 102, 300) to detect the size. The driving means (10) is driven and controlled in the sub-scanning direction from a predetermined home position (HP) according to the document size detected by the means (101, 102, 300), and a signal read by exposure scanning during the driving is image forming means. A control means (300) for outputting to (200) is provided. The symbols in parentheses are the corresponding elements of the examples described later.

[0006]

According to this, when the manual sheet feeding system is used, the traveling body first moves forward when the use of the manual sheet feeding system is detected, and when the transfer paper is completely set in the manual sheet feeding system, the traveling body is moved. It has moved to a predetermined position. After that, when the image forming instruction is issued, the traveling body moves back to detect the document size, and when the backward movement is completed, the traveling body moves forward to perform exposure scanning corresponding to the size of the document. No visible image is formed on the outside, and the wasteful use of the developer is eliminated. in addition,
Since the traveling body is driven only one way (reverse drive) from the image formation instruction until the image formation is started, the traveling body forward drive is started to detect the document size after the image formation instruction is issued. The time until the start of image formation is shorter than that in the case of performing. Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

[0007]

1 is a block diagram of a digital copying machine according to an embodiment of the present invention.
Document reading apparatus 100 and laser printer 200 shown in FIG.
Composed of and. The contact glass 1 for placing a document (not shown) in the document reading device 100 is
Illuminated by the light sources 2a and 2b, the reflected light (document image) from the read document is imaged on the light receiving surface of the CCD image sensor 9 via the mirrors 3, 4, 5, 6, 7 and the lens 8. The light source 2 (2a, 2b) and the mirror 3 are mounted on a traveling body (scanner) 10 that moves the lower surface of the contact glass 1 in parallel with the contact glass 1 in the sub-scanning direction (left and right direction in FIG. 1), and the mirror 4, 5 is the running body 1
It is mounted on a traveling body 11 that moves in the sub-scanning direction at a speed of 1/2 in conjunction with 0. Main scanning is performed by solid-state scanning of the CCD image sensor 9, and the original image is CCD.
The image is read by the image sensor 9, and the entire surface of the original is scanned by moving the optical system as described above. The reading density is 16 pixels / pixel for both main and sub scanning.
The size is set to mm, and it is possible to read documents of A3 size (297 mm x 420 mm). HP in the figure indicates the home position of the traveling body, and P indicates the maximum sub-scanning position.

FIG. 2 is a block diagram showing the configuration of the signal processing system of the image reading apparatus 100. In the figure, 12 is a sensor driver, 9 is a CCD image sensor, 13 is an amplifier, 14 is an A / D converter, 15 is a shading correction circuit, 16 is an MTF correction circuit, 17 is a main scanning variable magnification circuit, and 18 is a halftone. Is an output circuit, 101 is a size detection circuit, and 102 is a parallel-serial conversion circuit.
As described above, the image signal read at the sampling density of 16 pixels / mm is first amplified to a predetermined voltage amplitude which is the amplifier 13, and then the A / D conversion circuit 14
It is converted into digital data of several gradations (64 gradations in this embodiment) per pixel. Then, shading correction for correcting unevenness in illuminance of the light sources 2a and 2b, variation in sensitivity between the respective elements of the CCD image sensor 9, and MT of the optical system.
After the F correction and various conversion processes (binarization process) required for final output such as halftone processing are similarly performed in the printer unit, the necessary signal form is output. When performing size detection, the output from the shading correction circuit is fetched into the size detection circuit 101, and the signal obtained by the size detection circuit 101 is converted into the parallel-serial conversion circuit 1.
The data is converted and output in 02, the details of which will be described later.

Referring again to FIG. 1, the laser printer 200
Will be described. The laser printer 200 includes a laser writing system, an image reproducing system, and a paper feeding system. The laser writing system includes a laser output unit 21, an imaging lens 22 and a mirror 23. Inside the laser output unit 21, there is provided a laser diode, which is a laser light source, and a polygon mirror (polygon mirror) that rotates at a high speed and a constant speed by an electric motor. The laser light output from the laser writing system is applied to the photosensitive drum 25 of the image reproducing system. Around the photosensitive drum 24,
Charging charger 25, eraser 26, developing unit 2
7, a transfer charger 28, a separation charger 29, a separation claw 30, a cleaning unit 31, etc. are provided.
A beam sensor (not shown) for generating a main scanning synchronization signal (MSSYNC) is arranged at a position near the one end of the photosensitive drum 24 where the laser beam is emitted.

The image reproduction process in this laser printer will be briefly described. The peripheral surface of the photosensitive drum 24 is uniformly charged to a high potential by the charging charger 25.
When the peripheral surface is irradiated with laser light, the potential of the irradiated portion is lowered. Since the laser light is controlled to be turned on / off in accordance with black / white of recording / reproduction, the potential distribution corresponding to the recorded image on the peripheral surface of the photoconductor drum 24 by irradiation of the laser light,
That is, an electrostatic latent image is formed. When the portion on which the electrostatic latent image is formed passes through the developing unit 27, toner adheres according to the level of the potential, and the electrostatic latent image becomes a visualized toner image. The recording sheet 32 is fed from the cassette to the portion where the toner image is formed at a predetermined timing and overlaps the toner image. This toner image is transferred to the recording sheet 32 by the transfer charger 28, and then separated from the photosensitive drum 24 by the separation charger 29 and the separation claw 30. The separated recording sheet 32 is conveyed by the conveyor belt 34.
The sheet is conveyed by, and heated by a fixing roller 35 having a built-in heater, and then discharged onto a sheet discharge tray 36.

In this embodiment, there are two paper feeding systems. One of the paper feeding systems is provided with an upper paper feeding cassette 33a and an openable / closeable manual paper feeding table (manual paper feeding table) 33c. The upper paper feeding cassette 33a or the manual paper feeding table 33c is provided.
The recording sheet set at is fed by the feeding roller 37a. The other paper feed system is provided with a lower paper feed cassette 33b, and the recording sheets in the lower paper feed cassette 33b are fed by a paper feed roller 37b. Then, the recording sheet fed from any one of the sheet feeding rollers is temporarily stopped while being in contact with the registration roller 38, and is fed to the photosensitive drum 24 at a timing synchronized with the progress of the recording process. The manual paper feed tray 33c is an openable paper feed tray mounted on the main body of the laser printer 200, and a sensor 33s for detecting the open / closed state of the manual paper feed tray is provided on the main body of the laser printer 200. Although not shown, recording sheet size sensors for detecting the sizes of the recording sheets 32a and 32b stored in the cassettes 33a and 33b are provided, respectively.

FIG. 3 is a block diagram showing a schematic configuration of an electric control system of the entire digital copying machine. This electric control system is composed of a main control unit 300, a storage unit 310, an optical control unit 320, an AC control unit 330, an operation control unit 340, and the like. The main control section 300 includes various sensors 302 (opening / closing detection sensor 3 for the manual paper feed tray) provided in each section of the main body 100.
(Including 3 s) to control loads such as solenoids and motors of each part. The optical control unit 320 controls a lens motor that drives the lens 8, a scanner motor that performs optical scanning, and the like based on inputs from an APS sensor and an encoder for detecting the position of the traveling body (scanner), and an AC control unit. Three
Reference numeral 30 controls AC loads such as the heaters of the exposure lamps 2a and 2b and the fixing roller 35, the main motor, the developing motor, the conveyance motor, and the paper feeding motor. The operation control unit 340
The operation & display board 41 performs key operation reading and display control. Although not shown, the operation & display board 41 is provided with a key for instructing print start.

A method of detecting the position of the document placed on the contact glass 1 or the size of the document in the image reading apparatus 100 before starting the above-described document reading operation will be described below. Conventionally, the standard for placing a document on the contact glass 1 has been different for each device. From the operator's point of view, one that uses one of the four corners such as the front right corner as a reference, what is called the center reference such as aligning the center of one side of the original with the middle of the right side or the left side, and the contact glass There are various types of devices such as those that detect the position and read it, no matter where it is placed. In this embodiment, as shown in FIGS. 4 and 5, the corner on the front right side is set as the reference point A (see FIG. 4). In the figure, 1 is a contact glass, 39 is a document pressure plate, 40 is a scale, 41
Is an operation and display board, 42 is a document, arrow X is the main scanning direction, and arrow Y is the sub-scanning direction.

As a method of setting the original document, after the original document is placed at the reference position, it is pressed by the original document pressure plate, or while the pressure plate is left open, or an automatic document feeder (ADF) is attached. In some cases, the document is used to automatically convey the document to the reference position, or even if the ADF is mounted, the ADF is used as a pressure plate. When the ADF is used to automatically feed the document, the size of the document can be detected in the ADF. This embodiment relates to a device for detecting the position or size of a document when the ADF is used as the document pressure plate 39 or when the ADF is not mounted. Further, the method of detecting the document position and the document size according to the present embodiment performs the detection operation by performing a prescan before the normal document reading operation or the copy operation.

As the detection element, the CCD image sensor 9 used when performing a normal reading operation is used as it is. The principle of detection is that the filter 43 has a high reflectance of the pressure plate 39 during normal copying, cuts only the reflected light of the pressure plate 39 during detection, and can sufficiently transmit the reflected light of the background portion of the document.
By using this (shown in FIG. 11), the position or size of the document is detected from the difference between the outputs of the CCD plate 9 and the CCD image sensor 9 at the background of the document. Naturally, even if the pressure plate is opened during copying of a book document or the like, reflected light does not occur outside the document area, so the filter 4 described above is used.
The same result as in the case where only the reflected light of the pressure plate 39 is cut by using No.

Next, a detailed description will be given. In this embodiment, the light source 2
Fluorescent lamp used as (2a, 2b) (fluorescent lamp 2)
FIG. 6 shows the spectral distribution characteristics of. As is apparent from this figure, in the case of the fluorescent lamp 2, the central emission wavelength is 550 nm, and other than that, 410 nm, 440 nm, 480 nm, 580 nm,
There is a relatively strong energy distribution at 620 nm. On the other hand, as the original pressure plate 39 or the ADF belt functioning as the original pressure plate 39, a belt colored yellow having a high spectral reflectance at 500 nm or more as shown in FIG. 7 is used.

With the fluorescent lamp 2 and the original pressure plate (ADF belt) 39 colored in yellow, reflected light almost like a white belt can be obtained during normal original reading. Therefore, the background of the document is not darkened and the output recording sheets other than the document are not blackened. The fluorescent lamp 2 and the original platen 3
9 is used, an optical filter 43 having a transmission characteristic with a center transmission wavelength of 420 nm as shown in FIG. 8 is arranged in the optical path for detecting the original position or the original size. As a result, the reflected light of the document pressure plate 39 at the time of detection is cut, and the reflected light (400 nm to 480 nm) of the white background document is detected by the CCD.
It is received by the image sensor 9 and the density difference between the original pressure plate 39 and the area outside the original when the pressure plate is opened is taken.

FIG. 9 is a light receiving sensitivity characteristic diagram of the CCD image sensor 9. As can be seen from this figure, the CCD image sensor 9 has a light receiving sensitivity in the range of 400 nm to 480 nm, but the amount of light is reduced by inserting the filter 43 as described above. In view of this, in the present embodiment, the above-described light amount down is covered by changing some conditions depending on whether the normal document is read or the document position or document size is detected, so that stable detection operation can be performed.

As a first method for compensating for the decrease in light quantity, there is a method for increasing the light quantity of the fluorescent lamp. However, when the fluorescent lamp 2 and the optical filter 43 described above are used, the exposure amount to the CCD image sensor 9 drops to about 1/20.
It is not possible to cover the decrease in the amount of light by increasing the amount of light by the fluorescent lamp.

As a second method, there is a method in which the charge storage time of the CCD image sensor is lengthened and the exposure amount thereof is increased. With this method, since there is no particular limitation in increasing the exposure amount, it is possible to cope with a reduction in the light amount of about 1/20. This second method alone may be used, or it may be combined with the method of increasing the light amount of the fluorescent lamp 2.

In this embodiment, the light amount of the fluorescent lamp 2 remains unchanged, and the accumulation time is extended 16 times, whereby the optical filter 4
It covers the decrease in the light amount due to 3. However, in the normal document reading operation, particularly in the laser printer 20 as in the present embodiment.
When used by connecting to 0, the horizontal sync signal (HSYNC) of the read raster scan is synchronized with the main scan sync signal (MSSYNC) obtained from the beam sensor of the laser printer,
Since the synchronization of HSYNC is set to be the storage time of the CCD image sensor 9, it cannot be changed as it is. However, since the printout operation is not performed when detecting the document position or document size,
The HSYNC is removed from the MSYNC, and the image reading apparatus 100
Switch to HSYNC created within. Further, the transfer speed of the CCD image sensor 9 is also changed according to this.
That is, if it is possible to deal with this by switching the pixel clock (VCK) that is the basic clock of the circuit that performs image processing, even if the timing changes between normal document reading and document position or document size detection. The CCD image sensor 9 can be driven by the same circuit, and image data can be taken by the same circuit.

Since the printout is not performed, it is necessary to prevent the image reading device 100 from outputting the image signal output period signal (FGATE) to the external device such as the printer 200 when the document position or the document size is detected. .. However, this does not cause a problem if the system controller accurately controls the normal time and the detection time to prevent malfunction.

Further, if the charge storage time of the CCD image sensor is increased 16 times, the reading pitch in the sub-scanning direction is also 1.
6 times more. This is because the reading pitch in the sub-scanning direction is proportional to the charge accumulation time and the moving speed of the optical system. That is, the charge accumulation time is increased 16 times and the moving speed is reduced to 1/16.
If it is doubled, the reading pitch will be 16 dots / mm as it is, but the resolution and accuracy are not required at the time of the document position or document size detection operation. Rather, it is an extra time before the document reading operation, so it is necessary to make it a little faster. The detection accuracy of about 1 mm is sufficient, and if the fixed size is recognized, about 2 to 3 mm is sufficient. For this reason, in this embodiment, at the time of detection, the document reading movement speed is doubled. Therefore, the reading pitch is set to 2 mm and 16 dot / mm does not change in the main scanning direction.

In the image reading apparatus 100 of this embodiment, the CC
The output of the D image sensor 9 is amplified to a predetermined amplitude, and the gain of the amplifier at that time is determined for each scan. This is because the change in the amount of light due to the temperature of the tube wall of the fluorescent lamp 2 and the deterioration over time are taken into consideration. A white plate serving as a reference is provided in between, and the gain is set so as to amplify the output of the CCD image sensor 9 by the reflected light of the reference white plate to a predetermined voltage level.

Further, after the gain is determined, shading correction for correcting the light distribution in the main scanning direction of the fluorescent lamp 2 and the sensitivity variation of each element of the CCD image sensor 9 is performed. Output of each sensor (A / D converted digital data) 1
It writes in memory corresponding to one sensor element. After the reading of the original is started, the shading correction is performed based on the output data of the CCD image sensor and the white plate read data of each element.

In this embodiment, 2 lines of main scanning (2 rasters) are used for gain setting, and about 32 lines (32 rasters) for writing shading data in the memory.
During this period, the largest (white) data is written.

The gain setting and the writing of the shading data are also performed when the document position or the document size is detected. Since the reading pitch in the sub-scanning direction is as large as 2 mm as described above, the gain setting 2 raster and shading are performed. When writing 32 rasters for data writing, the width of the reference white plate needs to be 68 mm. Traveling body 10
The distance from the document reading start position to the original reading position must be 68 mm or more.

Normally, the gain is set and the shading data is written with a width of about 2 to 5 mm, but only one raster can be read at the time of size detection with this width. Lowest
Since 2 rasters are required for gain setting and 2 rasters for writing shading data, the minimum width of the reference plate is 8 mm. Therefore, it is necessary to change the reading width or the reading raster number of the reference plate during normal operation and size detection.

FIG. 10 is an enlarged sectional view showing an example of the arrangement of the reference plate. As shown in the figure, the first reference white plate 44 is set on the side edge that is the reference edge of the contact glass 1,
Further, a second reference white plate 45 that is wider than the first reference plate 44 is set adjacent to the side edge. The first reference white plate 44 is used during normal document reading, and the second reference white plate 45 or both the first reference white plate 44 and the second reference white plate 45 are used when detecting the document position or document size.

In the case where the image reading apparatus 100 is linked with the laser printer 200 as in the present embodiment, when the document is read, the print key is turned on to start feeding the recording sheet, and when the recording sheet reaches the registration roller, Then, the recording sheet is stopped, the fluorescent lamp 2 of the reading device is turned on, and the traveling body 10 starts to move. The reference white plate 44 is read at a distance so as to stabilize the speed of the traveling body 10 and the light amount of the fluorescent lamp 2, and when entering the original area, the original image data is binary / black or white desired by the printer 200. The output to the laser printer 200 as an image signal is started. As described above, when the writing system of the laser printer 200 is started, laser writing and development are performed. When the toner image is formed on the photoconductor 24, the recording sheet on standby is sent out by the registration roller 38 so as to be aligned with the toner image, and transfer, separation and fixing are performed, and the copy operation is completed.

On the other hand, when the document size is detected, the laser printer 200 does not operate, so that the reading device may be operated as a single unit. As described above, the reference white plate 44,
Since the reading width of 45 becomes long, the operation sequence is slightly changed. That is, when the print key is turned on, the fluorescent lamp 2 is first turned on, but since the moving speed is faster than normal and the reading of the reference white plates 44 and 45 is started earlier, the light quantity of the fluorescent lamp 2 is stabilized, It takes a sufficient time for the traveling body to start after the fluorescent lamp 2 is turned on, and the traveling body is started when the amount of light becomes stable.
Since the scanning range means that all the originals in the contact glass are detected, the entire surface of the contact glass 1 is scanned.

Next, the insertion of the above-mentioned optical filter 43 will be described with reference to FIGS. 11 and 12. This optical filter 43 may be placed in any part of the optical path, but in order to make the shape of the optical filter as small as possible, in this embodiment, the optical filter 43 is composed of the mirror 7 and the lens 8 as shown in FIG. It is placed in between. The optical filter 43 is rotatable, and is inserted into the optical path by raising the optical filter 43, and retracted from the optical path by tilting it.

FIG. 12 is a view showing another arrangement example of the optical filter 43, in which the optical filter 43 is arranged between the lens 8 and the CCD image sensor 9. And the optical filter 43
Is movable up and down, and by moving up and down, the optical filter 43 is inserted into the optical path or retracted from the optical path. Also in this case, the optical filter 4
No. 3 is smaller and less susceptible to flare.

The optical filter 43 is removed when reading the original,
It is designed to be inserted into the optical path only when detecting the document size. The timing of insertion is until the fluorescent lamp 2 is turned on after the print key is turned on and the running body 10 is started, but before the printer key is turned on or the reference white board 4 is inserted.
There may be a period after reading 4, 45 until the traveling body moves to the document area. When the reference white plates 44 and 45 are inserted after being read, the charge accumulation time of the CCD image sensor 9 remains normal before the insertion, and 1 after the insertion.
It will be 6 times.

The above are the conditions for detecting the document size in this embodiment. Next, how the image reading device is operated under such conditions to retrieve the document size information will be described.

Image data is used for detection. That is, the sensor driver 12, the amplifier 13, the A / D converter 14, and the shading correction circuit 15 shown in FIG. 2 can use the same circuits as in the normal operation. Using the image data that has been subjected to shading correction, the original plate area (including the area outside the original when the platen is opened) and the background area of the original are separated to determine the original area. There are two methods for this determination. is there.

The first method of discrimination is to set a threshold level of a certain value between the density of the original platen 39 and the density of the white background of the original, and the density data of several gradations / pixels is set to 2 at this threshold level. This is a method of extracting the document area code by digitizing. This binarization method is simple and the circuit is simple, but in the case of an original having relatively high transparency such as tracing paper or the second original, or when the spectral reflection distribution of the original is close to the original platen 39. , Original pressure plate 39
The concentration level is close to that of. Therefore, an appropriate threshold level cannot be determined due to variations in the amount of light, variations in the sensitivity of the CCD image sensor 9, and the like, and detection accuracy becomes a problem.

The second method of discrimination is a method of detecting the edge portion of the document by monitoring the density level difference with the adjacent pixel.
With this method, even if the density levels of both the original pressure plate 39 and the original are varied, it is possible to detect if there is a difference in density between pixels, so that there is a feature that most types of originals can be handled. Therefore, although the detection circuit using the second method is constructed in this embodiment, the first method described above can be applied in the same manner.

The read raster R when the manual feed tray 33c of this embodiment is closed is as shown in FIG. 13 (a). When the main scanning direction is X, the sub-scanning direction is Y, and the original placement reference point A is the origin (0, 0), the area of the original is point P ₁ , point P ₂ , point Q _{1 as} indicated by the broken line. It can be recognized as an area surrounded by four points of the point Q _2. Here, if the original 42 has an ordinary quadrangle and the standard is the point A, the point Q ₂ (X ₂ ,
It is only necessary to detect Y ₂ ). But the other 3
Detecting points is not too difficult. Further, the points P ₁ ′, the points P ₂ ′, the points Q ₁ ′ and the points Q ₂ ′ at the four corners when the original 42 is inclined as shown by the solid lines in the figure.
It is also possible to detect In this embodiment, the points P ₁ ,
Point P ₂ , point Q ₁ and point Q _2, that is, point X ₁ , point X ₂ ,
An example of detecting the points Y ₁ and Y ₂ will be shown.

Since the image data is raster scanning, it is input as one-dimensional data in the X direction (main scanning direction). FIG. 14 shows a time chart of HSYNC, MVALID, VCLK and image data. As shown in the figure, one raster is read at the HSYNC cycle. At this time, the MVALID signal indicating the range of the contact glass, that is, the effective image range is provided, and the image data during this period is used. In this embodiment, about 4800 pixels are input per raster in synchronization with VCLK. This signal is a 6-bit 64 gradation / pixel signal, where the whitest level is 0 and the blackest level is 63.

For the edge detection by the adjacent pixels, a method using a Laplacian filter or the like by adjacent pixels is known as a portable method. However, the purpose of the detection here is to obtain the boundary between the document background and the document pressure plate 39, the density of the document pressure plate 39 is almost uniform, and the document background is also uniform near the boundary. From the above, the density difference at several pixels apart is taken, and when a similar density difference appears continuously, it is set as one candidate for the boundary between the document background and the document pressure plate 39. In this embodiment, a difference in density from a distance of 4 pixels is calculated, and when three pixels having a density equal to or higher than a predetermined value continue for three pixels, the boundary is set as the candidate for the boundary.

FIG. 15 is a diagram for explaining an example of recognition of the boundary between the document background and the document pressure plate. In the case of this example, the image density of a is 5, the image density of b is 4, the image density of c is 5, the image density of d is 7, the image density of e is 36, the image density of f is 42, Assume that sampling data is obtained in which the image density of g is 45 and the image density of h is 44. As described above, since the density difference between the sampling data 4 pixels apart is determined, the density difference between the pixel a and the pixel e is 31, and the density difference between the pixel b and the pixel f is 38 and c. The density difference between the pixel and the g pixel is 40, and the density difference between the d pixel and the h pixel is 37. If the density difference of 5 or more continues for three or more times, it will be extracted as a candidate for the boundary portion, so that the pixel between the pixel of d and the pixel of e becomes the candidate of the boundary portion.

Referring again to FIG. 13A,
The edge that appears first in each raster is the candidate for X ₁ , and the edge that appears last is for X ₂ . The candidates for X _{1 and} the candidates for X ₂ are taken out from each raster and compared with the candidates for X _{1 and} the candidates for X ₂ left up to the preceding raster, respectively. Leaving less than X _1, leaving a larger X _2, X _1, X ₂ remaining in the sub-scanning completion point, the X _1, X ₂ for indicating the original area of FIG. 13 (a). Although there is a density change in the original 42, this method causes no problem X ₁ ,
X ₂ can be detected. When these X ₁ and X ₂ are retained and retained, if the Y value at that time is retained and retained, the coordinates of the points P ₁ ′ and P ₂ ′ in FIG. 13A can be detected. ..

Next, for the detection of Y ₁ and Y ₂ , the signal for extracting the candidate of each raster end is used as it is. If there is at least one edge candidate in one raster, it is assumed to be the original area. There is also a method of taking the density of adjacent pixels in the Y direction as well, but in that case, it is raster scanning. Therefore, since it becomes necessary to perform the line delay using the memory, the circuit becomes slightly complicated, but it is performed only in one dimension in the X direction as in the present embodiment.

When the traveling body moves in the Y direction, the Y address at the time when a raster having one or more end candidates first appears is held. This is Y ₁ . Y when the traveling body further advances and there is no end in the raster
Hold the address. When the traveling body further advances,
The edge may appear again. This is because there is a black band in the manuscript or a shadow of the binding part of the book manuscript. In that case, Y when the end part disappears again
Retake the address value. That is, finally, the Y address when the document edge disappears is taken out as Y ₂ from the document section. Also at this time, if the X ₂ candidate is extracted from the raster when Y ₁ is extracted, the coordinates of the point Q ₁ ′ are obtained, and if the X ₁ candidate is extracted from the raster when Y ₂ is extracted, the point P ₂ ′ is obtained.
It becomes the coordinates of.

FIG. 16 shows an example of a circuit for realizing such a detection method. This figure is an example of detecting X ₂ and Y ₂ described above. A 6-bit image signal (DATA) input with respect to LCLK and a signal delayed by VCLK4 synchronization, that is, a signal separated by 4 pixels from this signal are taken out, and the difference detection circuit 46 takes the absolute value of the difference between these values,
Further, the comparison circuit 47 compares it with a certain reference value THR (corresponding to a density difference of 5 in the example shown in FIG. 15). When the comparison result is larger than this reference value, a signal which becomes "H" is output, and when this is "H" continuously for VCLK3, "H" is finally output as an end candidate signal.

First, how to take out the X size is MVALI
X-direction address counter (X-count) that counts up from 0 in synchronization with VCLK while D is "H"
48 is provided, and its output is put into the D-F / F circuit 49.
When the edge candidate signal changes from "L" to "H" within the period of MVALID = "H", the D-F / F circuit 49 changes the value of X-count 48 at that time to the next value. Step D-
Put in the F / F circuit 50. This D-F / F circuit 50 is M
When the edge candidate signal changes from "L" to "H" within the period of VALID = "H", X-c at that time
The value of ount48 is output to the D-F / F circuit 49 of the next stage. When the edge candidate signal changes from “L” to “H” multiple times during the period of MVALID = “H”, the value is updated each time the change occurs. When detecting X ₁ , do not update. Then, the D-F / F circuit 50 of the second stage
Outputs the X address of the final end candidate in the raster every time the MVALID = “H” period ends. The output value is compared with the address value held up to the previous raster by the comparator 51, and the larger one is selected,
It is held by the D-F / F circuit 52 at the final stage.
Therefore, the finally remaining value is X ₂ (X size). When X ₁ is taken out, it can be obtained by leaving the smaller value in each raster.

The method of extracting the Y size is MVA for each raster.
Using the J-KF / F circuit 53 that is cleared (Q = “L”) during the period of LID = “L”, the end candidate signal is MV.
It is set (Q = “H”) when there is even one during the period of ALID = “H”, and this output (Q) is DF / F at the end of MVALID = “H”. F circuit 5
Take out at 4.

The Y address is MVALID while the FGATE signal representing the image effective period in the sub-scanning direction is "H".
It is given in Y-count, which counts up from 0 in synchronization with. This Y address is used as the D-F / F circuit 5
When the QR output of No. 4 changes from "L" to "H", that is, from a raster with an edge to a raster without an edge, it is taken out to the D-F / F circuit 54 and this QR is output.
When there are a plurality of changes from "L" to "H", the value is finally updated and the value finally obtained is the point Y ₂ (Y size). Q = “L” to “H”
When the address is fetched by the change (QR = “H” to “L”) and the value is not updated by the second and subsequent changes, the point Y ₁ is obtained.

Here, the difference between the pixels separated by 4 pixels is taken, but the number of pixels may be 3 pixels or less, or 5 pixels or more. However, in the case of the present embodiment, for the convenience of CCD driving, different analog processing systems (from CCD output to A / D conversion) are used for even-numbered pixels and odd-numbered pixels, so even-numbered pixels and odd-numbered pixels are used. Since there is less error in comparing each other, we chose even-numbered ones. Further, the circuit is constructed by the same principle by using a signal obtained by binarizing a threshold value between the document background level and the document pressure plate level as described above, instead of the method of detecting the end portion. it can. Further, even when the end portion is detected by using a two-dimensional spatial filter instead of simply taking a one-dimensional difference, the same circuit can be configured except for the filter portion.

In the case of the present embodiment, the Y size has a value of a unit of 2 mm, the X size has a maximum value of a pixel unit, and the counter output can take twice as many units. Usually, it is considered that the required accuracy of X and Y is the same,
Also in the embodiment, the lower and lower bits of the X-count are cut to 2 mm.
Take out as a unit. In this embodiment, as shown in FIG.
The X size and the Y size are converted into serial data by parallel-serial conversion, and are sequentially read by a read pulse from the CPU. At this time, the bit length (total of X and Y sizes) and the transfer order must be determined in advance.

As another method, there is a method of sending in parallel to each of X and Y, or in parallel using a bus common to X and Y. Also, the code is moved by discriminating into a fixed size such as A4 and B4. However, the serial method can be realized with the simplest configuration. In addition, in order to prevent malfunctions due to dirt on the pressure plate and adhesion of dust, the method of detecting the document position by monitoring the density difference with neighboring pixels, if both the pixels for which the density difference is seen are darker than a certain level, It is also possible not to regard it as the end regardless of the difference. Further, by using the document position or document size signal detected as described above, the output timing at the time of printout or facsimile communication can be corrected according to the document position.

That is, in this embodiment, the image signal is transmitted to an external device (for example, printer or facsimile control).
When outputting to, the image effective signal in the main scanning direction and the image effective signal in the sub-scanning direction are output at the same time as the image signal, and this is received by the printer speed or the facsimile controller. The positional deviation can be corrected by correcting X ₁ and Y _{1 in} FIG. 13A and performing laser writing or transmission. Further, during main scanning after detecting the document position or document size, the read image valid signal (MVALID) can be corrected by shifting by X ₁ and Y ₁ . Moreover, FIG.
By detecting P ₁ ′, P ₂ ′, Q ₁ ′, Q ₂ ′ shown in 3 (a),
The correction of the skew displacement of the original document 42 is also possible by using the memory. That is, after storing the image signal in the memory, when reading it, the address for memory access is processed by computing the angles of P ₁ ′ and Q ₁ ′. The processing of this address is constant, and can be realized by calculating the address processing pattern by the CPU or the like after detecting the original and applying it to the address circuit.

17 and 18 show control flowcharts of the main control section 300 for controlling the entire digital copying machine. This routine starts when the power is turned on. First, the operator function is selected (step 1: hereinafter, the word step is omitted in parentheses). Examples of this selection function include setting of magnification, density control, number of copies, paper size, automatic paper selection, and automatic magnification selection. Next, when the sensor 33s for detecting the opening / closing of the manual paper feed table (manual paper table) 33c is on (manual paper table open), the printer 200 and the image reading apparatus 100 are desynchronized, and the scanner motor is driven to move forward. The body (scanner) 10 is moved to the maximum sub-scanning position (position P shown in FIG. 1) (2, 3, 4). On the other hand, when the sensor 33s for detecting the opening / closing of the manual feed tray 33c is off (close the manual feed tray), the traveling body 10 is set at a predetermined position (home position HP) (2, 5). In either case, the light sources 2a and 2b are kept off during the movement.

When the print key is pressed while the manual feed tray is open, the charge storage time of the CCD image sensor is multiplied by 16 (6, 7, 8). In this state, the printer and the scanner are already out of sync in step 3.
Next, an optical filter having the above characteristics is inserted in the optical path (9), the scanner speed is set to 240 mm / s (10), the light source is turned on (11), and the scanner is started (13). ). At this time, the scanner is driven back.

When the print key is pressed while the manual feed tray is closed, it is determined whether the automatic paper selection function or the automatic magnification selection function is selected (6, 7, 1).
3). If the automatic paper selection function or automatic magnification selection function is selected, unsynchronize the printer and scanner,
16 times the charge storage time of CCD image sensor (1
4). Next, an optical filter having the above characteristics is inserted into the optical path (15), the scanner speed is set to 240 mm / s (16), the light source is turned on (17), and the scanner is started (18). ). At this time, the scanner is in forward drive.

On the other hand, if it is determined in step 13 that the automatic paper selection function or automatic magnification selection function is not selected, the printer and scanner are synchronized (19).
And the scanner speed is 120 × (100 / magnification α) mm
/ S (20), start feeding the printer (21), determine whether the paper has reached the registration rollers, and after confirming that the paper has reached the registration position, turn on the power. (22, 23), the scanner starts (24). The scanner is forward drive.

Subsequent to step 18, the document position is detected (27) and the document size is determined (28).
Then, after the scanner is driven back to the home position, it is judged whether the paper is selected or the magnification is selected (29, 30). As a result, if the magnification is selected, the magnification is set (3).
1) If the paper is set, the paper is set (32),
Go to step 19. In addition, the position detection of the document (27),
In the determination of the document size (28), the same process as the size detection described above is performed.

Subsequent to step 12, the document position is detected (25) and the document size is determined (26), and the process proceeds to step 19. In the document position detection (25) and the document size determination (26), the same processing as the size detection described above is performed, but it is considered that the scanning in the Y direction is the reverse scanning to the size detection described above. There is a need. This will be described below.

FIG. 13B shows the read raster R when the manual feed tray 33c is open. This corresponds to the read raster R when the manual feed tray 33c is closed as shown in FIG. When the manual feed tray 33c is open, the size is detected during the backward movement of the scanner, so the scanning start point is shown in FIG.
It becomes the A1 (0, 6720) point shown in (b). Also, Y
Since the scanning in the direction is opposite to that when the manual feed tray 33c is closed, the address in the Y direction needs to be down-counted from the maximum address (6720) to the address 0. Therefore, the boundary point first detected in the Y direction after the start of scanning corresponds to the boundary point Y ₂ when the manual feed stand 33c is closed,
The finally detected boundary point corresponds to the boundary point Y ₁ when the manual feed stand 33c is closed. It should be noted that the detection of the boundary point and the scanning and detection in the X direction are exactly the same as when the manual feed table 33c is closed.

The flowchart will be described again.
Image reading is started following step 24 (33), and it is determined whether image writing to the printer has started (34). After that, the registration rollers are started (35), and a copying process such as transfer, separation, and fixing is performed (36). This copy process (3
6) also includes re-driving of the scanner after image formation. Until the designated number of copies are completed, S19-S24, S33-
The process of S36 is repeated (37). When the designated number of copies are completed, the process returns to step 1.

FIG. 19 is a time chart showing the operation of the scanner when there is a copy start instruction after the manual feed tray is changed from the closed state to the open state. To briefly explain this, first, when the manual feed tray is opened, the scanner motor starts rotating in the forward direction. The encoder detects the rotation (speed) of the motor, and after reaching the target speed, the motor rotates at a constant speed. Further, the moving distance of the scanner is calculated by the encoder input, and the rotation of the motor is stopped to stop the scanner when the target position is reached. By pressing the print key, the scanner motor starts rotating in the reverse direction,
When the scanner runs for a preset time, the motor rotates at a constant speed. The above-described document detection is performed while the motor is rotating at a constant speed.

As described above, in this embodiment, when the manual feed tray is changed from the closed state to the open state, the sensor detects this and moves the traveling body of the image reading apparatus 100 to the maximum sub-scanning position (P). When a copy start instruction is given in this state, the traveling body 100 is scanned from the maximum sub-scanning position P toward the home position HP under a predetermined condition for detecting the document size, and the document size is detected by the signal obtained at this time. .. Then, when the document size is detected, the image is formed by scanning the traveling body within the range corresponding to the detected size of the document and reading the image as in the conventional case.

[0064]

As described above, according to the present invention, when the manual feed system is used, the traveling body first moves forward when the use of the manual feed system is detected, and the transfer paper is set in the manual feed system. By the time the operation is completed, the traveling body has moved to a predetermined position. After that, when the image forming instruction is issued, the traveling body moves back to detect the document size, and when the backward movement is completed, the traveling body moves forward to perform exposure scanning corresponding to the size of the document. No visible image is formed on the outside, and the wasteful use of the developer is eliminated. In addition, the drive of the traveling body is one-way (return drive) from the image formation instruction until the image formation is started.
Since it is only the case, the forward drive of the traveling body is started to detect the document size after the image formation instruction is issued.
The time to start image formation is shortened.

[Brief description of drawings]

FIG. 1 is a document reading device 100 and a laser printer 2.
10 is a side view showing a schematic mechanism of a digital copying machine configured by 00.

2 is a configuration block diagram of a signal processing system of the image reading apparatus 100. FIG.

FIG. 3 is a block diagram showing a schematic configuration of an electric control system of the entire digital copying machine.

FIG. 4 is a schematic perspective view of the document reading apparatus 100.

5 is a plan view showing a scanning area and a reference point A of the document reading apparatus 100. FIG.

FIG. 6 is a light source 2 (2a, 2b) of the document reading apparatus 100.
3 is a graph showing the spectral distribution characteristics of a fluorescent lamp used as a.

FIG. 7 is a graph showing a spectral reflectance of a document pressure plate.

FIG. 8 is a graph showing transmission characteristics of the optical filter 43.

FIG. 9 is a graph showing a light receiving sensitivity characteristic of the CCD image sensor 9.

FIG. 10 is an enlarged cross-sectional view showing an example of the arrangement of reference plates.

FIG. 11 is a schematic side view of an optical system of the document reading apparatus 100 showing an insertion position of an optical filter 43.

FIG. 12 is a schematic side view of the optical system of the document reading apparatus 100 showing an insertion position of the optical filter 43, which is arranged differently from the example shown in FIG.

13A and 13B are top views of a contact glass showing a reading raster R of the image reading apparatus 100, FIG. 13A is a reading raster when the manual feed table is closed, and FIG. 13B is a read when the manual feed table is open. Each raster is shown.

FIG. 14 is a time chart of HSYNC, MVALID, VCLK and image data.

FIG. 15 is a block diagram showing data values for explaining an example of recognition of a boundary portion between a document background portion and a document pressure plate.

FIG. 16 is a circuit diagram showing an example of a size detection circuit.

FIG. 17 is a flowchart of a main controller 300 that controls the entire digital copying machine.

FIG. 18 is a flowchart of a main control unit 300 that controls the entire digital copying machine.

FIG. 19 is a time chart showing the operation of the scanner when the manual feed tray 33c is open and a copy start instruction is issued.

[Explanation of symbols]

100: image reading device (image reading means) HP: home position P: maximum sub-scanning position 101: size detection circuit 102: parallel-serial conversion circuit 200: laser printer (image forming means) 33c: manual feed tray 37a: paper feed Roller (33c, 37a: manual feed system) 33s: manual feed tray open / close detection sensor (detection sensor) 41: operation & display board (instruction means) 300: main control unit (control means) (101, 102, 300: Size detection means)

Claims (1)

[Claims] 1. An image reading unit for driving a traveling body equipped with an illuminating unit extending in the main scanning direction in the sub-scanning direction to expose and scan an original, and reading a signal corresponding to an original pixel; a signal read by the image reading unit. Size detecting means for detecting the size of the original;
In response to the signal read by the image reading means, an image forming means for forming an image on a transfer paper fed to a predetermined position at a predetermined timing; an instruction means for instructing the image formation; Manual paper feed system for feeding paper to a predetermined position at a timing; Detection means for detecting use / non-use of the manual paper feed system; When the detection means detects use of the manual paper feed system, the traveling body is driven to the maximum sub-scanning position When the image forming instruction is given by the controlling means and the instructing means, the traveling body is driven and controlled from the maximum sub-scanning position in the direction of the predetermined home position, and the signal obtained by exposing and scanning the original at the time of driving is sent to the size detecting means. The output is output, and the traveling body is driven and controlled in the sub-scanning direction from a predetermined home position according to the document size detected by the size detecting means, and a signal read by exposure scanning during the driving is output to the image forming means. Digital image forming apparatus including: control means.